The Role of the Insular Cortex in Dysphagia

Abstract

Recent data indicate that dysphagia may occur following unilateral cortical stroke; however, the elucidation of specific cytoarchitectonic sites that produce deglutition disorders remains unclear. In a previous study of unilateral cortical stroke patients with dysphagia, Daniels et al. proposed that the insula may be important in swallowing as it was the most common lesion site in the patients studied. Therefore, 4 unilateral stroke patients with discrete lesions of the insular cortex were studied to further facilitate understanding of the role of the insula in swallowing. Dysphagia, as confirmed by videofluoroscopy, was evident in 3 of the 4 patients; all had lesions that involved the anterior insula, whereas the only patient without dysphagia had a lesion restricted to the posterior insula. These data suggest that the anterior insula may be an important cortical substrate in swallowing. The anterior insula has connections to the primary and supplementary motor cortices, the ventroposterior medial nucleus of the thalamus, and to the nucleus tractus solitarius, all of which are important regions in the mediation of oropharyngeal swallowing. Therefore, discrete lesions of the anterior insula may disrupt these connections and, thereby, produce dysphagia.

Lesion Location Predicts Transient and Extended Risk of Aspiration After Supratentorial Ischemic Stroke

“…28,29 A recent intracortical microstimulation study found that stimulation of the anterior sector of the dorsal insula triggered swallowing, mouthing, and chewing in monkeys. 30 Oroalimentary behavior, including motor automatisms, has been described during epileptic seizures originating in this part of the insula.…”

“…31 Stroke patients with discrete lesions of the anterior insula have been shown to suffer from dysphagia in small case studies. 28,29 Furthermore, sensory and motor signaling from and to various areas might be mediated by the insula (eg, interacting with the oropharynx and the esophagus). 32 A magnetoencephalographic study demonstrated consistent long-lasting activation of the insular cortex before swallowing.…”

“…28,47 Damage to both areas might therefore cause a more severe and longer-lasting risk of aspiration. Additionally, there is evidence that the insulo-opercular transition zone represents a primary gustatory cortex.…”

Enhancing effects of flavored nutritive stimuli on cortical swallowing network activity

“…However, a large body of physiological evidence indicates that the cerebral cortex plays a fundamental role, not only in initiation (5,36), but also in regulation and modulation, of deglutition (18,29,35). Furthermore, clinical observations have long documented the development of swallowing disorders due to cerebrovascular accident (13,37) or traumatic brain injury (7,12) in the absence of brain stem involvement (9,14). In humans, recent cortical mapping studies using functional brain imaging (4,10,15,16,24,28,33,45,47) show that volitional swallowing bilaterally activates a number of cerebral cortical areas, including cingulate gyrus, prefrontal and sensory/motor cortices, insula, and precuneus, collectively considered to represent the "cortical swallowing network.…”

Normal Swallowing and Functional Magnetic Resonance Imaging: A Systematic Review

“…These investigations have characteristically started with a disordered neurologic group (i.e., poststroke population) and combined both anatomical brain-imaging techniques (still pictures of the brain) such as computerized tomography (CT) and/or magnetic resonance imaging (MRI) with a swallowing assessment to correlate damaged brain areas with the presence or type of dysphagia observed. The vast majority of clinical studies have focused on the effects of stroke on swallowing [2][3][4][5][6][7][8][9][10][11][12][13][14][15] This systematic review summarizes studies that have explored the neurophysiology of swallowing in healthy adults using fMRI. The goal of a systematic review is to gather and present objectively the current status of research in a particular area of interest.…”